N-enrichment at the GaAs 1− xN x/GaAs(0 0 1) interface: microstructure and optical properties

Abstract

We have investigated the growth, the microstructure and the optical properties of the GaAs 0.97N 0.03/GaAs interface. Epilayers were grown at 520–550°C using trimethylgallium, dimethylhydrazine and arsine on GaAs(0 0 1) vicinal surfaces. A 5–6 nm thick layer of GaAsN with N-enrichment is clearly seen by cross-sectional transmission electron microscopy at the interfacial region. The nitrogen composition at the interface is twice that of the bulk epilayer (close to 1.6%) as shown by photoluminescence spectroscopy (PL) and high resolution X-ray diffraction. The PL data of several samples shows two peaks located at 1–1.1 and 1.2–1.3 eV associated with the interfacial region and the bulk layer, respectively. We discuss several mechanisms for the nitrogen enrichment by comparing the GaAsN film thickness. The step/terrace surface morphology of GaAs before growth is probably the key parameter.